Fool’s Gold: An Illustrated Critique of Differential Privacy

Jane Bambauer, Krishnamurty Muralidhar, and Rathindra Sarathy · 16 Vand. J. Ent. & Tech. 701

Abstract

Differential privacy has taken the privacy community by storm. Computer scientists developed this technique to allow researchers to submit queries to databases without being able to glean sensitive information about the individuals described in the data. Legal scholars champion differential privacy as a practical solution to the competing interests in research and confidentiality, and policymakers are poised to adopt it as the gold standard for data privacy. It would be a disastrous mistake.

This Article provides an illustrated guide to the virtues and pitfalls of differential privacy. While the technique is suitable for a narrow set of research uses, the great majority of analyses would produce results that are beyond absurd—average income in the negative millions or correlations well above 1.0, for example.

The legal community mistakenly believes that differential privacy can offer the benefits of data research without sacrificing privacy. In fact, differential privacy will usually produce either very wrong research results or very useless privacy protections. Policymakers and data stewards will have to rely on a mix of approaches—perhaps differential privacy where it is well suited to the task and other disclosure prevention techniques in the great majority of situations where it isn’t.